1. Field of the Invention
The present invention relates to a shutter device for a camera, an image display apparatus or the like.
2. Description of Related Art
A focal plane shutter of the kind having a plurality of divided blade groups swingably held by parallel link mechanisms each of which consists of two arms is popularly used for a camera or the like. The parallel link mechanisms used for focal plane shutters can be divided into a long arm type and a short arm type. In the long arm type, the base end parts of the arms are swingably mounted on one of two sides of a shutter aperture formed in a shutter base plate. The arms straddle the shutter aperture. The blade groups are interlinked by the fore end parts of the arms on the other side of the shutter aperture. In the short arm type, the base end parts of the arms are swingably mounted on one of two sides of the shutter aperture. The arms interlink the blade groups by their fore end parts on the same one side of the shutter aperture without straddling the shutter aperture.
Among the known focal plane shutters, so-called vertical travel focal plane shutters are most popularly used. Of the vertical travel focal plane shutters, the long arm type focal plane shutter is arranged, as disclosed in Japanese Laid-Open Utility Model Publication No. Sho 35-29651, to swingably hold the blade groups by the arms on the opposite side across the shutter aperture with respect to the base end parts of the arms. Because of this arrangement, the arms become longer than the width of the shutter aperture.
In the long arm type, the arm swinging angle required for opening and closing the shutter aperture with the.blade groups is small. Therefore, the amount of displacement of the blade groups in the direction of orthogonally intersecting the traveling direction of the blade groups for opening or closing the shutter aperture, i.e., in the direction of width, becomes small. The small amount of displacement is advantageous for reduction in size of the shutter. However, in a case where the number of blades to be held by the two arms is arranged to be three or more, the arrangement results in a complex structure. Besides, the use of long arms increases the inertia of the shutter blade unit consisting of the blade groups and the arms. The large inertia is a disadvantage for a high speed travel of the shutter blades.
Therefore, as a result of the recent trend of increasing a shutter speed for an exposure and making flash light emission synchronizing time shorter, the long arm type focal plane shutter has come to be seldom used.
On the other hand, the short arm type focal plane shutter has come to be more popularly used. Although it is more disadvantageous than the long arm type in respect of reduction in width, the short arm type is advantageous in the following points. The two arms are arranged not to straddle the shutter aperture and to be able to swingably hold many blades on the side of the shutter aperture located close to their base end parts. Besides, the inertia of the shutter blade unit can be minimized by arranging the arms to be as short as possible.
FIGS. 19 and 20 show the arrangement and dimensions of the parts of a short arm type focal plane shutter. FIG. 19 shows the short arm type focal plane shutter as in a state of having completed preparation for a travel. FIG. 20 shows it as in a state obtained upon completion of the travel. In the case of this shutter device, the base end part of a first leading-curtain arm 106 and that of a second leading-curtain arm 107 are swingably mounted on shafts 101d and 101e which are provided on a shutter base plate 101 having a shutter opening 101a. These two leading-curtain arms 106 and 107 interlink and carry in a swingable manner a slit forming blade 102 and four cover blades 103, 104, 105 and 105xe2x80x2 which jointly form a leading curtain consisting of five blades. These blades are interlinked to form a parallel link by using blade caulking dowels 108a to 108e and 109a to 109e. The base end part of a first trailing-curtain arm 114 and that of a second trailing-curtain arm 115 are swingably mounted on shafts 101f and 101g on the shutter base plate 101. The trailing-curtain arms 106 and 107 swingably interlink and carry a slit forming blade 110 and three cover blades 111, 112 and 113 which jointly form a trailing curtain consisting of four blades. These blades are interlinked to form a parallel link by using blade caulking dowels 116a to 116d and 117a to 117d. 
On each of the leading- and trailing-curtain sides, the blade caulking dowels are simply allocated in a moderately arcuate line. The first and second arms are arranged to come close to each other side by side when the leading and training curtains are in a state of overlapping each other. The shutter device described above is hereinafter called a first example of prior art.
A shutter device disclosed in Japanese Laid-Open Utility Model Publication No. Hei 6-26896 is arranged to permit reduction in size by adding a third auxiliary arm (and may be a fourth auxiliary arm) to the two arms in view of that a parallel link consisting of the two arms does not easily permit reduction in size. The shutter device is arranged such that, when the shutter blades are overlapping, support parts of the first and second arms where the slit forming blades are carried by these arms are located within a stowing area between a viewfinder and an aperture window, while the third arm which carries other covering blades is arranged to be located outside of the stowing area, so that an outside lateral dimension of the shutter device can be lessened.
To have three arms within a small space, each arm is arrange to be thin, this shutter device is arranged as follows. In the blade overlapping state, the center of swing of the base end part of a third arm enters in between the center of swing of the base end part of a first arm and the caulking dowel of a third cover blade, and the caulking dowel of the third cover blade on the first arm enters in between the center of swing of the base end part of the first arm and the third cover blade. That shutter device is called a second example of prior art.
Japanese Laid-Open Utility Model Publication No. Hei 6-26897 disclosed another shutter device. The shutter device is arranged to permit reduction in size and to increase the durability thereof. For this purpose, one of two main arms is connected to one of the pivotal support parts of each blade on the other main arm while the other pivotal support part is connected to the other main arm and also to an auxiliary arm. The shutter device is called a third example of prior art.
Japanese Utility Model Registration No. 2501747 disclosed a shutter device. The shutter device consists of slit forming blades arranged to be driven by a first parallel link, cover blades arranged to be driven by a second parallel link. An interlinking distance on the slit forming blade of the first parallel link is arranged to be longer than an interlinking distance on the cover blades of the second parallel link in such a way as to keep the parallelism of the slit forming blades and yet to reduce a space from the shutter aperture to the base end part of each parallel link. The shutter device is called a fourth example of prior art.
Japanese Laid-Open Patent Application No. Sho 53-143314 disclosed a shutter device arranged to reduce the size of a long arm type shutter by reducing a space for stowing shutter blade groups in an overlapped state. For this purpose, arm blades are arranged to function both as arms of a parallel link and as cover blades for blocking light from a shutter aperture. The arm blades are arranged to carry slit blades (slit forming blades) in conjunction with arms and also to cover spaces between other cover blades. The shutter device is called a fifth example of prior art.
Generally, it is advantageous for reduction in size (particularly in width) of a shutter device (focal plane shutter) to arrange the number of blades in each of divided blade groups to be fewer. With the number of blades arranged to be fewer, an area to be occupied by blade interlinking parts becomes less. However, the arrangement to have a fewer number of blades of the blade group results in a less amount of mutual overlapping of blades in covering a shutter aperture of a predetermined size. The less amount of overlapping makes it difficult to adequately block light from the shutter aperture.
In the first example of prior art, the length of arms is short. Besides, the number of leading curtain blades is as many as five. As a result, the blade caulking dowels which are simply aligned are spaced at very short distances. The short spacing distance lessens the design latitude of setting positions where cover blades can be carried in a swingable manner. Therefore, interference takes place within the blade unit. Referring to FIG. 20, the interference includes the interference of the periphery of the base end part 106b of the first arm 106 with the periphery of the second arm 107 located around the blade caulking dowel 109e or the periphery of the cover blade 105xe2x80x2, and interference of the periphery of the first arm 106 located around the blade caulking dowels 108e with a peripheral part of the second arm 107 or the periphery of the cover blade 104 or 105 located around the blade caulking dowels 104 and 105. Since the dimension of the shutter aperture in the direction of travel of the shutter blades is fixed, it is impossible to increase the arm swinging angle to a predetermined distance, without increasing the arm swinging angle. Besides, it becomes difficult to adequately keep the overlapping amount of the cover blades over the slit forming blades with the shutter device in a state of spreading blades. The possible extent of reduction in size of the shutter device is thus limited.
In a case where a four-blade arrangement applied to the trailing shutter curtain is likewise applied also to the leading shutter blades, as shown in FIG. 20, the amount of mutual overlapping of blades obtained when the trailing curtain is spread decreases to about 2 mm. Therefore, even if the width of each blade is widened to a maximum degree allowable by the blade stowing space with the leading curtain blades in their mutual overlapping state, the spacing distance becomes shorter with the blade caulking dowels in a simply aligned state. Then, under the restriction of the blade caulking dowels, the latitude allowed to setting the swingably carrying positions of the cover blades decreases like in the case of the five-blade arrangement mentioned above. As a result, interference takes place within the blade unit. For example, as shown in FIG. 19, the interference taking place includes interference of the periphery of the base end part 114b of the first arm 114 with the periphery of the second arm 115 and that of the cover blade 113 located around the blade caulking dowel 117d, and interference of the periphery of the first arm 114 located around the blade caulking dowels 116d with a peripheral part of the second arm 115 or that of the cover blade 112 located around the blade caulking dowels 117c. Therefore, it is impossible to secure a desired amount of blade overlapping of 4 mm, as the blade width cannot be widened more than 1 mm at the most on the side opposite to the direction of blade travel. The arrangement thus dose not permit much reduction in size of the shutter device. (The arrangement of the blade caulking dowels will be described in detail later herein at Para. vi).
In the second example of prior art (the shutter device disclosed in Japanese Laid-Open Utility Model Publication No. Hei 6-26896), a third arm is additionally arranged to carry the cover blade group. The arrangement results in a structure more complex than the ordinary parallel link mechanism using two arms like in the first example of prior art. The operating resistance of the parallel link mechanism increases. The inertia of the blade unit also increases. Besides, the arrangement to have three arms within a limited space makes each arm thinner to weaken the strength of the arm. In addition to these shortcomings, the arrangement to have the support parts of the first and second arms where the slit forming blade is carried located within a stowing area between a viewfinder and an aperture window, when the blades are in an overlapped state, shortens an interlinking distance on the slit forming blade in the parallel link. The shorter interlinking distance makes it difficult to keep an exposure slit at an adequate rate of parallelism.
The third example of prior art (the shutter device disclosed in Japanese Laid-Open Utility Model Publication No. Hei 6-26897) has the same shortcomings as the second example of prior art, namely, the addition of the third (auxiliary) arm for supporting the cover blade group results in a structure more complex than the ordinary parallel link mechanism using two arms like in the first example of prior art, increases the operating resistance of the parallel link mechanism, and also increases the inertia of the blade unit. Although the number of arms is increased to disperse loads on the arms, the arrangement to have three or more arms within a space severely reduced by reduction in size results in use of thinner arms at the expense of strength of the arms.
In the fourth example of prior art (the shutter device disclosed in Japanese Utility Model Registration No. 2501747), two parallel link mechanisms are arranged for one blade unit, and a third arm (and further a fourth arm) is additionally used for supporting the cover blade groups. This results in a structure more complex than the ordinary parallel link mechanism using two arm like in the first example of prior art, increases the operating resistance of the parallel link mechanism, and also increases the inertia of the blade unit. Besides, the arrangement to have three or more arms within a space severely reduced by reduction in size results in use of thinner arms at the expense of strength of the arms.
Each of the first to fourth examples of prior art described above is a short arm type shutter device. However, the end parts on the sides of arm base ends of the slit forming blades of both the leading and trailing curtains (particularly the end parts of slit forming edges on the sides of the arm base ends) are interlinked in such a way as to fittingly penetrate the arms of the blade unit and are not to intrude into the movable range of the driving pins provided on the blade driving lever arranged to drive these arms. This is because, when the shutter blade unit is spread, if the end part of one slit forming blade on the arm base end side is intruding into the movable range of the driving pin on the side of the other blade, there arise the following two problems.
One problem lies in that, in charging the shutter, to retain an adequate light blocking state by not opening the shutter aperture 201a, as shown in FIG. 21, the leading curtain 202 shifts to a state of covering the shutter aperture (a spread state) prior to the trailing curtain 210. At this time, the above-stated intruding state might cause the driving pin 220a to interfere with the end part 210b of the slit forming blade of the trailing curtain on the arm base end side.
The other problem lies in that, in a case where a function of keeping the trailing curtain 210 at a travel start position fails to be performed despite of charging the shutter due to some trouble or malfunction as shown in FIG. 22, the driving pin 221a of the trailing curtain driving lever might come to interfere with the end part 202b of the slit forming blade of the trailing curtain 210 on the arm base end side.
Meanwhile, for each of the leading and trailing curtains, arrangement to allow the end part of the slit forming blade on the arm base end side to intrude into the movable range of the driving pin of the blade driving lever connected to the arm of its unit of blades when the blades are in an overlapped state brings about no problem. However, none of the first to fourth examples of prior art (short arm type shutter devices) has such arrangement.
On the other hand, a shutter device which is of the same type as the fifth example of prior art (a long arm type shutter device disclosed in Japanese Laid-Open Patent Application No. Sho 53-143314) can be arranged to allow, for each of the leading and trailing curtains, the end part of the slit forming blade on the arm base end side to intrude into the movable range of the driving pin of the blade driving lever connected to the arm of its unit of blades when the blades are in an overlapped state. For example, FIGS. 12 to 14 of Japanese Laid-Open Patent Application No. Sho 53-143314 show such arrangement.
However, the above-stated arrangement is nothing else but an unintended result of structural arrangement for actuating cover blades by means of pin-slot coupling. The disclosed arrangement is not intended to take the advantage of that the long arm type has a small action angle of arms to allow a larger latitude in setting the movable range of the driving pin of the blade driving lever and much less intended to reduce the size of the shutter in the lateral dimension thereof. By the way, in the case of a short arm type shutter device, if the movable range of the driving pin is excessively close to a corner of the shutter aperture, the allocation of the blade groups becomes difficult. Therefore, if the number of blade groups to be carried by two arms is arranged to be three or more, there arises the above-stated problems including that the structural arrangement becomes complex, a large resistance to actuating the light blocking blades by pin-slot coupling, and a disadvantage for a high speed shutter travel due to a large inertia of the blade unit having the long arms.
Therefore, in the case of each of the second to fifth examples of prior art, a camera, for example, can be hardly arranged to have an exposure time shorter than 1/4000 sec or to have a flash device synchronizing time shorter than 1/200 sec. Further, a shutter charging energy increases for obtaining the same shutter curtain speed. Arrangement to solve these problems results in an increase in size of the camera or makes it difficult to increase the film frame transport speed when the camera is in a continuous photo-taking mode.
In view of the problems of prior art described above, it is a first object of the invention to provide a shutter unit which is simply arranged to permit reduction in size and particularly reduction in dimension in the direction orthogonally intersecting the traveling direction of shutter blades. It is a second object of the invention to provide a shutter device arranged to be capable of securing a sufficient blade overlapping amount for blocking light, to have a small inertia of blade units, to have excellent working efficiency and to be suited for a high speed operation.
To attain these objects, a shutter device arranged in one aspect of the invention comprises a shutter base plate having a shutter aperture, a plurality of shutter blades, and an arm member arranged to swing on a predetermined shaft provided on the shutter base plate, the arm member being connected to each of the plurality of shutter blades to cause the shutter blades to travel over the shutter aperture when the arm member swings on the shaft. In the shutter device, with a distance to the shaft from a connection part located farthest from the shaft among connection parts where the shutter blades are connected to the arm member assumed to be D, and the dimension (length) of the shutter aperture in the direction of travel of the shutter blades assumed to be A, the following condition is satisfied:
0.78 Axe2x89xa6Dxe2x89xa60.90 A.
In the shutter device, with the maximum angle of swing of the arm member assumed to be xcex8, the following condition is satisfied:
80xc2x0xe2x89xa6xcex8xe2x89xa694xc2x0.
The shutter device further comprises a second arm member arranged to swing on a shaft which differs from the predetermined shaft and to be connected to each of the plurality of shutter blades. In the shutter device, with a distance between the shaft of the arm member and the shaft of the second arm member assumed to be E and the dimension (length) of the shutter aperture in the direction of travel of the shutter blades to be A, the following condition is satisfied:
0.33 Axe2x89xa6Exe2x89xa60.39 A.
In the shutter device, with a distance from an end face of the shutter base plate at which the center of swing of the arm member is provided to the end face of the shutter aperture assumed to be B, the shutter device satisfies the following condition:
0.56 Axe2x89xa6Bxe2x89xa60.70 A.
In the shutter device, with a distance from an end face of the shutter base plate at which the center of swing of the arm member is not provided to the end face of the shutter aperture assumed to be C, the shutter device satisfies the following condition:
0.24 Axe2x89xa6Cxe2x89xa60.30 A.
A shutter device arranged in another aspect of the invention comprises a shutter base plate having a shutter aperture, a plurality of shutter blades, and an arm member arranged to swing on a predetermined shaft which is provided as a center of swing on the shutter base plate, the arm member being connected to each of the plurality of shutter blades to cause the shutter blades to travel over the shutter aperture by swinging on the shaft. In the shutter device, with the maximum angle of swing of the arm member assumed to be xcex8, the following condition is satisfied:
xe2x80x8380xc2x0xe2x89xa6xcex8xe2x89xa694xc2x0.
Further, in the shutter device, with a distance to the shaft from a connection part located farthest from the shaft among connection parts where the shutter blades are connected to the arm member assumed to be D, and the dimension (length) of the shutter aperture in the direction of travel of the shutter blades assumed to be A, the following condition is satisfied:
0.78 Axe2x89xa6Dxe2x89xa60.90 A.
A shutter device arranged in a further aspect of the invention comprises a shutter base plate having a shutter aperture, a plurality of shutter blades, a first arm member arranged to swing on a predetermined shaft provided on the shutter base plate as a center of swing, the first arm member being connected to each of the plurality of shutter blades, and a second arm member arranged to swing on a shaft which differs from the predetermined shaft, the second arm member being connected to each of the plurality of shutter blades, the plurality of shutter blades being arranged to travel over the shutter aperture when the first and second arm members swing respectively on the shafts. In the shutter device, with a distance between the shaft of the first arm member and the shaft of the second arm member assumed to be E and the dimension (length) of the shutter aperture in the direction of travel of the shutter blades assumed to be A, the following condition is satisfied:
0.33 Axe2x89xa6Exe2x89xa60.39 A.
A shutter device arranged in a further aspect of the invention comprises a shutter base plate having a shutter aperture, first, second, third and fourth shutter blades, and a first arm member arranged to swing on a predetermined shaft provided on the shutter base plate, the first arm member being connected to, in the order of from the farthest to the nearest to the center of swing of the first arm member, the first, second, third and fourth shutter blades, one by one, and arranged to cause the four shutter blades to travel over the shutter aperture when the first arm member swings on the shaft. In the shutter device, among distances of connection parts where the shutter blades are connected to the first arm member, with respect to a line segment connecting to the shaft the connection part where the first shutter blade is connected to the first arm member, the distance of the connection part connecting the third shutter blade to the first arm member is the longest.
The shutter device further comprises a second arm member which is connected to the first, second, third and fourth shutter blades.
In the shutter device, the second arm member is provided with a recessed part which is formed in such a shape that effectively prevents the second arm member from interfering with the connection part where the third shutter blade is connected to the first arm member.
A shutter device arranged in a further aspect of the invention comprises a shutter base plate having a shutter aperture, a plurality of shutter blades, a first arm member arranged to swing on a predetermined shaft provided on the shutter base plate as a center of swing, the first arm member being connected to each of the plurality of shutter blades, a second arm member arranged to swing on a shaft which differs from the predetermined shaft, the second arm member being connected to each of the plurality of shutter blades, and a driving member arranged to drive the first arm member to swing on the center of swing. In the shutter device, a shutter blade which determines the shape of the shutter aperture among the plurality of shutter blades has the blade end thereof, on the side where the shafts are located, arranged to be located within the driving area of the driving member when all of the plurality of shutter blades are in an overlapped state and to part from the driving area when the shutter blade is in a state of being driven by the driving member.
Further, in the shutter device, the plurality of shutter blades constitute a trailing curtain shutter unit which is arranged to close the shutter aperture, and the shutter device further comprises a leading curtain shutter unit which is arranged to bring the shutter aperture from a closed state to an open state before the trailing curtain shutter unit is driven by the driving member.
The shutter device further comprises second driving means arranged to drive an arm member which is connected to a plurality of shutter blades of the leading curtain shutter unit.